Eating ultra-processed foods harms your gut—here’s how inflammation takes hold

New research exposes how ultra-processed foods trigger inflammation and disrupt gut bacteria, potentially driving diabetes, cancer, and neurological diseases. Here’s why you might rethink your diet.

Study: The Detrimental Impact of Ultra-Processed Foods on the Human Gut Microbiome and Gut Barrier. Image Credit: Rimma Bondarenko / Shutterstock.com

Ultra-processed foods (UPFs) adversely impact the equilibrium of the gut microbiome by promoting a pro-inflammatory environment, reducing microbial diversity, and increasing intestinal permeability, all of which contribute to inflammation and dysbiosis. In a recent Nutrients study, researchers further explore the impact of UPFs on gut permeability and the microbiome.

Characteristics of UPFs

UPFs are defined as industrial formulations with five or more ingredients, often including additives, sugars, oils, fats, salt, and preservatives. They often lack dietary fiber, which is crucial for digestive and microbiota health.

Several industrial procedures are used in the production of UPFs to ensure their long shelf life and enhance their taste, texture, and convenience. The Maillard reaction, for example, is a common processing technique that improves sensory attributes like color, flavor, and texture; however, Maillard reaction products can potentially function as prooxidants and carcinogens.

Extrusion is another method that can lead to lipid oxidation, followed by the degradation of unsaturated fatty acids and the formation of free radicals. Hydrogenation, which is typically used when making margarine, can also increase low-density lipoprotein (LDL) cholesterol levels.

Individuals who eat meals later in the day are more likely to consume UPFs than early eaters. In fact, one recent meta-analysis reported how a high intake of UPFs adversely impacts sleep duration and quality, irrespective of age.

The adverse impacts of UPFs on the gut microbiome

The consumption of UPFs may lead to the proliferation of pro-inflammatory microbial strains and reduced microbial α-diversity in the gut. UPF intake has also been shown to reduce the production of short-chain fatty acids (SCFAs) and other protective gastrointestinal metabolites. These alterations in the gut microbiome can collectively lead to systemic inflammation and oxidative stress, both of which are characteristic features of various chronic diseases.

As compared to individuals who consume low amounts of UPFs, those who consume high amounts of UPFs exhibit higher levels of potentially harmful bacteria in their microbiome, some of which include Granulicatella, Blautia, Carnobacteriaceae, and Bacteroidaceae. High UPF consumption has also been associated with lower levels of Roseburia and Lachnospira, both of which produce SCFAs.

Emulsifiers used in UPFs can prevent the proliferation of beneficial bacteria with anti-inflammatory properties, which can increase gut permeability and bacterial translocation into the bloodstream. Many UPFs are also high in saturated fat, which can increase the risk of developing cardiovascular disease (CVD).

High-fat diets can lead to low levels of Eubacterium rectale, Bacteroides, Verrucomicrobia, Bifidobacterium, and Clostridium coccoides, as well as greater proliferation of Firmicutes, Proteobacteria, and pro-inflammatory cytokines. Saturated fats also promote excessive lipid accumulation in the liver and hyperinsulinemia.

Human health and UPF-induced dysbiosis

Diabetes

UPF-induced microbiome alterations have been shown to increase an individual’s risk of developing cardiometabolic disease. For example, a greater ratio of Firmicutes to Bacteroidetes influences the development of type 2 diabetes (T2D). Moreover, individuals consuming diets rich in UPFs exhibit a lower presence of Akkermansia muciniphila, which improves insulin levels, sensitivity, and weight control.

Inflammatory bowel disease

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD), arise due to inflammation of the intestinal mucosa. An imbalance in the gut microbiota of IBD patients could enhance the permeability of the intestinal barrier and increase immune system activation.

The colon of both CD and UC patients is often characterized by reduced α-diversity and low levels of anti-inflammatory bacterial species, including Roseburia hominis and Akkermansia muciniphila. In IBD patients, increased intestinal inflammation can arise due to alterations in bile acid metabolism, SCFA production, and tryptophan metabolism.

Cancer

The Western diet is a key factor that contributes to the rising incidence of colorectal cancer (CRC). CRC-associated dysbiosis is characterized by the loss of anti-inflammatory bacteria, reduced microbiome diversity, and increased pathobionts.

Among the primary species implicated in both adenomas and CRC are Bacteroides fragilis, Fusobacterium nucleatum, and Parvimonas micra. These pro-carcinogenic bacteria may produce various metabolites, such as reactive oxygen species or toxins that can cause DNA damage.

Neurological disorders

Cognitive function and mental health are closely linked to the composition of the gut microbiota through the ‘gut-brain axis.’ Changes in the gut microbiota may lead to psychopathological conditions such as Parkinson’s disease (PD) and Alzheimer’s disease (AD).

Major depressive disorder patients often exhibit reduced richness and diversity in the gut microbiota, including low levels of Bacteroidetes, Firmicutes, Actinobacteria, and Proteobacteria.

Conclusions

Additional studies are needed to determine the mechanisms by which the consumption of UPFs leads to gut dysbiosis and other chronic diseases. Nevertheless, the study findings emphasize the need for stricter regulations to ban the production of UPFs and enforce detailed labeling of food products that contain UPFs.